[Babel-users] FW: Loose ends with Babel

[Robert Lukan]

First of all, length of message is not so important after all. IMHO its better that you focus on other features of protocol.

Its true, I am using babel with serial link(ppp), and that is weird. In our project I would have to use RF modems(with central frequency around few ten MHz) with serial connectors, so speed will be 19200 or 38400 (simplex!). Thats the reason why I need a little as possible overhead and fast convergence (redundancy), unfortunately is that in contradiction. 
For beginning my plan task/plan is to create 3 nodes in loop, on main node will run also ospf which will be connected to cisco router. Right now I am writing some scripts so system will be "plug and play". So udev and shell script will take care of all new connections, it will create ppp,... I will also use ahcpd for autoconfiguration, I haven't test it yet. 

Few months ago, I tried to use AODVUU, on ethernet and wireless was working good, but on serial had some weird problems, so I have to change routing protocol.

I also testing OLSR. I will also make some tests, which protocol is better for wireless concerning bandwidth, time of convergence and stability! :)

If you have any other question, just ask me, I would be glad to tell what I am doing.  


Robert

-----Original Message-----
From: Juliusz Chroboczek [mailto:Juliusz.Chroboczek at pps.jussieu.fr]
Sent: Tue 7/8/2008 5:39 PM
To: Robert Lukan
Cc: babel-users at lists.alioth.debian.org
Subject: Re: [Babel-users] FW:  Loose ends with Babel
 

> From my point of view, it would be nice to have shorter massages,
> because I am using protocol on very limited bandwidth link,

Speaking about that, Robert, perhaps you could tell us more about your
setup?  You appear to be doing unusual stuff (I have trouble imagining
why you'd prefer PPP over serial to an Ethernet link).

> also is better to have shorter messages anyway.

I'll expand about that a little.

In Babel, I distinguish between messages and packets.  A message is
always 24 bytes long, and can carry one route, IPv4 or IPv6.

A packet consists of an 8-byte header followed with an arbitrary
number of messages followed by an optional cryptographic signature
(not implemented at the current time).

Now 24 bytes for an IPv4 route is overkill; it could fit in 8 bytes.
If you're compressing your PPP link, you don't care -- the extra data
are mostly zeroes, and will compress beautifully.  What's more, Babel
sends reachability data at very large intervals (there are other
mechanisms that ensure that the routing is mostly up-to-date usually,
and that even when it isn't, the network keeps working, although not
optimally).

The alternative would be to encode the Babel protocol as
``type-length-value'' triples.  This would make it more complex, more
difficult to parse, but would save quite a bit of space for IPv4
routes.  I'm not sure if it's worth my while; we'll only know when we
deploy larger Babel networks.

Regards,

                                        Juliusz

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